The last Much Ado in Regent's Park was one of those rare Shakespearean updates that fitted the play perfectly: an Edwardian country house party policed by Dad's Army, a distinctively English comedy that suited the park with no hint of the Sicilian music and festivities that marked National Theatre revivals, from Franco Zeffirelli's to Nicholas Hytner's.

Nor does Timothy Sheader's production, with surprise casting, follow an RSC route to colonial India or Latin America; it is staged simply and swiftly on a circular wooden platform decorated with two fruit trees , with a flurry of ladies in pastel-coloured silk gowns and soldiers in loosely Elizabethan leathers, boots and jerkins.

These costumes, by Deirdre Clancy, set a timeless, almost fairytale, mood that is ideal for the open air and proof again that the merry war of words between Beatrice and Benedick, in the aftermath of a military campaign and clouded by the evil machinations of a malcontent duke, can thrive in almost any context. And the self-denying lovers find their true interactive rhythm only when they see themselves in the shadow of a nearly ruined romance.

This shift from comedy to darkened plotting, as Benedick helps unravel the false accusations of infidelity against his kinsman Claudio, is echoed in the fading light between the tall, swaying trees in the park. But it's even more effectively marked in Sean Campion's performance, as he graduates from an Irish bearded buffoon to a concerned and considerate peacetime soldier.

He is partnered by Samantha Spiro's clownish, physically agile Beatrice who shows signs from the start that her spirited merriment will deepen into jocund wisdom. When each is deceived into thinking that the other knows of their true affections, they take refuge in bird noises and pratfalls.

Campion gurns goofily under the table, while Spiro – having flitted gracefully through the whole auditorium like the lapwing she's likened to – snaps a lemon tree branch, clucks like a chicken, gets a foot stuck in a fruit basket and finally falls out of the orange tree. Campion's comic statement is saved for the next scene, when he duly appears with a ridiculous hat and high-heeled shoes.

There's some odd microphoning of the actors, and a regrettable absence of live musicians, a loss not made entirely good by some fine singing from Tim Howar as Balthasar. Ben Mansfield is a dashing Claudio, Anneika Rose (a recent RSC Juliet) a touching Hero, though sexual chemistry is not this show's strongest suit.

The ridiculous watch is nicely led by Anthony O'Donnell's Dogberry. Simon Gregor is a loon of a Verges, Peter Bramhill's Borachio is notable and there's a marvellous Margaret from Annalisa Rossi. Philip Witcomb's design is finely lit by Simon Mills: a good, if not delirious, start to the season.